100. MoAbs. This last mobile group of the analyzed tumors showed comparable MUC-1 immunoexpression to ductal epithelial cells using both HMFG antibodies. Intraductal mucous secretion was also HMFG-1 and HMFG-2 positive. == Conclusions == Our results showed you will find two kinds of myoepithelial cells in PA. The first cellular group is usually represented by the different kinds of neoplastic myoepithelial eNOS cells and is HMFG-positive. The second one is HMFG-negative and represented by the neoplastic myoepithelial cells located round the ducts. Keywords:Salivary gland tumors, Pleomorphic adenoma, MUC-1 mucin, Human milk excess fat globule membrane, Myoepithelial cell == INTRODUCTION == Pleomorphic adenoma (PA) is the most common epithelial neoplasm arising in the salivary gland tissue; it is usually more frequently found in palate and is more common in males7. Racial differences among age, gender and location have been reported7,15,16. Human milk excess fat globule membrane (HMFG) is Saikosaponin B usually part of the apical cell membrane of the secretory mammary cells and it contains several differentiation antigens3. Two of them are HMFG-1 and HMFG-2 monoclonal antibodies (MoAbs), which are directed against the oligosaccharide side chains of glycoprotein components of this structure1. Anti-HMFG-1 and -2 comprise a set of Saikosaponin B monoclonal antibodies against the mucin 1 (MUC-1) protein and they happen to be found in breast malignant tumors25and in different benign tumors and malignancies from several organs1,5,6,8-13,17,27. The presence of HMFG membrane-derived antigens has been correlated with differentiation and prognosis13,26,27. To date, the presence of the epitopes of MUC-1 protein using HMFG-1 and -2 monoclonal antibodies has been demonstrated in several salivary gland tumors4,19,23,28. We were able to find only few studies around the expression of HMFG-1 in pleomorphic adenomas4,21,24. The aim of this study was to assess the immunoexpression of the PA neoplastic cells to MUC-1 protein using HMFG-1 and HMFG-2 MoAbs and to compare these results with those from normal salivary gland tissue. == MATERIAL AND METHODS == All examples of salivary gland tumors were collected from your files of the Clinical Oral Pathology Laboratory of the Facultad de Odontologa of Universidad Nacional Autnoma de Mxico in Mexico City, and PA cases were separated. Hematoxylin and eosin (H&E) stained slides were available in every case. All cases were microscopically examined and diagnoses were re-evaluated according to the World Health Business (WHO) International Classification of Salivary Gland Tumours2. Additional sections were stained with Periodic acidSchiff (PAS), alcian blue and Hales coloidal iron staining. Normal tissues from labial, submandibular and parotid salivary glands were used as controls. Cells in PAs were classified as epithelial and myoepithelial cells (MyECs). Epithelial Saikosaponin B cells were categorized as ductal and non-ductal cells, this last cellular set being created by metaplastic squamous cells, keratin pearls and cells in solid epithelial-like areas. MyECs were divided into two units: those found round the ductal structures were named classic myoepithelial cells (CMyECs); altered myoepithelial cells (MMyECs) were those found forming variable sized groups of spindle-shaped, plasmacytoid (hyaline) obvious cells. MyECs associated to chondroid, myxoid, hyaline or mucoid areas were also considered in the last group. MyECs in normal salivary glands were all considered as CMyECs. Methodology for synthesis and immunological features of the HMFG-1 and -2 MoAbs used in this study was described in detail by Arklie, et al.1(1981), Ceriani, et al.3(1979) and Taylor-Papadimitrou, et al.26(1981). Immunohistochemical detection of MUC-1 protein using HMFG-1 and HMFG2 MoAbs was conducted according to a previous publication14. Briefly, immunostaining was made in 5 solid, paraffin embedded slides, later rinsed with PBS answer. All sections were treated with H2O2for one hour to inhibit Saikosaponin B endogenous peroxidase activity and incubated for 10 min with 10% normal horse serum. Then, they were incubated overnight at 4C with HMFG-1 (1:100 dilution) and HMFG-2 (1:40 dilution) MoAbs and the avidin-biotin method was used. Peroxidase activity was detected using 3,3-diaminobenzidine tetrahydrocloride as the substrate and all slides were counterstained with Harris hematoxylin. Control was normal labial salivary gland tissue treated with the same techniques. Negative controls were made omitting the antibody. Immunostaining grading was the same used in.